Methods for flexible reference signal transmission with single carrier frequency domain multiple access (sc-fdma) and ofdma

ABSTRACT

A method for transmitting a discrete fourier transform (DFT) DFT-S-OFDM signal including frequency domain reference symbols is disclosed. The method comprises: determining to null a plurality of data symbols prior to DFT-spreading; performing DFT-spreading including the determined null data symbols; puncturing an interleaved output of the DFT-spreading; inserting reference symbols in a frequency domain of the punctured and interleaved DFT-S-OFDM signal; and transmitting the DFT-S-OFDM signal with inserted reference symbols to a receiver. The transmitted DFT-S-OFDM signal enables the receiver to apply zeros corresponding to the reference symbols to an interleaved input of DFT-despreading, and cancel interference due to the puncturing by using all outputs of the DFT-despreading.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage, under 35 U.S.C. § 371, ofInternational Application No. PCT/US2017/046195 filed Aug. 10, 2017,which claims the benefit of U.S. provisional application No. 62/373,126filed on Aug. 10, 2016 and U.S. provisional application No. 62/479,792filed on Mar. 31, 2017 the contents of which are hereby incorporated byreference herein.

BACKGROUND

In typical single-carrier frequency division multiple access (SC-FDMA)communications, such as is used in Long Term Evolution (LTE) uplinktransmission, the reference signal (RS) for data transmission can onlybe allocated in two time-domain symbol locations and no data symbols canbe transmitted in those locations. This overhead in terms of resourceusage is fixed for all users, regardless how different the channelconditions are among them, and cannot be changed dynamically based onchannel conditions and the need of services. For example, in low SINRand ultra-reliable application scenario, adding more RS will allow thereceiver to estimate the channel more accurately so the data can bedetected with a low error rate. On the other hand, in high SINR and highdata rate requirement scenario, some of the resources, which otherwisewould be used for transmitting RS, can be used to transmit the data.Therefore, it is desirable to design a transmitter and receiver schemethat allows flexibly in inserting the reference signal depending on eachusers link condition.

SUMMARY

A method for transmitting a Discrete Fourier Transform-Spread-OrthogonalFrequency Division Multiple Access (DFT-S-OFDM) signal includingfrequency domain reference symbols is disclosed. The method comprises:determining to null a plurality of data symbols prior to DFT-spreading;performing DFT-spreading including the determined null data symbols;puncturing an interleaved output of the DFT-spreading; insertingreference symbols in a frequency domain of the punctured and interleavedDFT-S-OFDM signal; and transmitting the DFT-S-OFDM signal with insertedreference symbols to a receiver. The transmitted DFT-S-OFDM signalenables the receiver to apply zeros corresponding to the referencesymbols to an interleaved input of DFT-despreading, and cancelinterference due to the puncturing by using all outputs of theDFT-despreading.

The number of reference symbols inserted may be based on a channelcondition associated with the receiver. For example if the channelcondition is relatively poor, the number of reference symbols insertedmay be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 10 is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 shows an example uplink frame format for one subframe inaccordance with an embodiment;

FIG. 3 shows a generic structure for the DFT-S-OFDM including multipleDFT-spread blocks;

FIG. 4 shows an example of resource allocation of reference signals fortwo users;

FIG. 5 shows an example of Transmitter and Receiver structures fordynamic RS insertion;

FIG. 6 shows the details of the IC block shown in FIG. 5;

FIG. 7 shows a different numerology within a subframe with a singlecarrier waveform;

FIG. 8 shows a different numerology within a subframe with an OFDMwaveform; and

FIG. 9 shows a transmitter and receiver block diagram for DFT-S-OFDMwith generalized frequency domain reference symbols.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN 104/, aCN 106/, a public switched telephone network (PSTN) 108, the Internet110, and other networks 112, though it will be appreciated that thedisclosed embodiments contemplate any number of WTRUs, base stations,networks, and/or network elements. Each of the WTRUs 102 a, 102 b, 102c, 102 d may be any type of device configured to operate and/orcommunicate in a wireless environment. By way of example, the WTRUs 102a, 102 b, 102 c, 102 d, any of which may be referred to as a “station”and/or a “STA”, may be configured to transmit and/or receive wirelesssignals and may include a user equipment (UE), a mobile station, a fixedor mobile subscriber unit, a subscription-based unit, a pager, acellular telephone, a personal digital assistant (PDA), a smartphone, alaptop, a netbook, a personal computer, a wireless sensor, a hotspot orMi-Fi device, an Internet of Things (IoT) device, a watch or otherwearable, a head-mounted display (HMD), a vehicle, a drone, a medicaldevice and applications (e.g., remote surgery), an industrial device andapplications (e.g., a robot and/or other wireless devices operating inan industrial and/or an automated processing chain contexts), a consumerelectronics device, a device operating on commercial and/or industrialwireless networks, and the like. Any of the WTRUs 102 a, 102 b, 102 cand 102 d may be interchangeably referred to as a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106/, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a Node-B, an eNode B,a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, anaccess point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104/, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneembodiment, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/ and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116_using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink(DL) Packet Access (HSDPA) and/or High-Speed uplink (UL) Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106.

The RAN 104/ may be in communication with the CN 106/, which may be anytype of network configured to provide voice, data, applications, and/orvoice over internet protocol (VoIP) services to one or more of the WTRUs102 a, 102 b, 102 c, 102 d. The data may have varying quality of service(QoS) requirements, such as differing throughput requirements, latencyrequirements, error tolerance requirements, reliability requirements,data throughput requirements, mobility requirements, and the like. TheCN 106/ may provide call control, billing services, mobilelocation-based services, pre-paid calling, Internet connectivity, videodistribution, etc., and/or perform high-level security functions, suchas user authentication. Although not shown in FIG. 1A, it will beappreciated that the RAN 104/ and/or the CN 106/ may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104/ or a different RAT. For example, in addition to being connectedto the RAN 104/, which may be utilizing a NR radio technology, the CN106/ may also be in communication with another RAN (not shown) employinga GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/ may also serve as a gateway for the WTRUs 102 a, 102 b, 102c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/ or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (10), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an embodiment,the WRTU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 10 is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 140 a, 140 b, 140c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 140 a, 140 b, 140 c may implement MIMO technology. Thus,the eNode-B 140 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 10, the eNode-Bs 140a, 140 b, 140 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 10 may include a mobility management entity(MME) 142, a serving gateway (SGW) 144, and a packet data network (PDN)gateway (or PGW) 146. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 142 may be connected to each of the eNode-Bs 140 a, 140 b, 140 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 144 may be connected to each of the eNode Bs 140 a, 140 b, 140 cin the RAN 104 via the S1 interface. The SGW 144 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW144 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 144 may be connected to the PGW 146, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1C as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative embodiments, the DLS may use an 802.11e DLS oran 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS)mode may not have an AP, and the STAs (e.g., all of the STAs) within orusing the IBSS may communicate directly with each other. The IBSS modeof communication may sometimes be referred to herein as an “ad-hoc” modeof communication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative embodiments, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

Another example of a communications system including the RAN 104 and theCN 106 is described herein. As noted above, the RAN 104 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 104 may also be in communication with theCN 106.

The RAN 104 may include gNBs (not shown), though it will be appreciatedthat the RAN may include any number of gNBs while remaining consistentwith an embodiment. The gNBs may each include one or more transceiversfor communicating with the WTRUs 102 a, 102 b, 102 c over the airinterface 116. In one embodiment, the gNBs may implement MIMOtechnology. For example, the gNBs may utilize beamforming to transmitsignals to and/or receive signals from the gNBs. Thus, a gNB, forexample, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs may implement carrier aggregation technology. For example, agNB may transmit multiple component carriers to the WTRU 102 a. A subsetof these component carriers may be on unlicensed spectrum while theremaining component carriers may be on licensed spectrum. In anembodiment, the gNBs may implement Coordinated Multi-Point (CoMP)technology. For example, WTRU 102 a may receive coordinatedtransmissions from multiple gNBs.

The WTRUs 102 a, 102 b, 102 c may communicate with the gNBs usingtransmissions associated with a scalable numerology. For example, theOFDM symbol spacing and/or OFDM subcarrier spacing may vary fordifferent transmissions, different cells, and/or different portions ofthe wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with the gNBs using subframe or transmission time intervals(TTIs) of various or scalable lengths (e.g., containing varying numberof OFDM symbols and/or lasting varying lengths of absolute time).

The gNBs may be configured to communicate with the WTRUs 102 a, 102 b,102 c in a standalone configuration and/or a non-standaloneconfiguration. In the standalone configuration, WTRUs 102 a, 102 b, 102c may communicate with the gNBs without also accessing other RANs (e.g.,such as eNode-Bs 140 a, 140 b, 140 c). In the standalone configuration,WTRUs 102 a, 102 b, 102 c may utilize one or more of the gNBs as amobility anchor point. In the standalone configuration, WTRUs 102 a, 102b, 102 c may communicate with the gNBs using signals in an unlicensedband. In a non-standalone configuration WTRUs 102 a, 102 b, 102 c maycommunicate with/connect to the gNBs while also communicatingwith/connecting to another RAN such as eNode-Bs 140 a, 140 b, 140 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs and one or more eNode-Bs 140 a, 140 b,140 c substantially simultaneously. In the non-standalone configuration,eNode-Bs 140 a, 140 b, 140 c may serve as a mobility anchor for WTRUs102 a, 102 b, 102 c and the gNBs may provide additional coverage and/orthroughput for servicing WTRUs 102 a, 102 b, 102 c.

Each of the gNBs may be associated with a particular cell and may beconfigured to handle radio resource management decisions, handoverdecisions, scheduling of users in the UL and/or DL, support of networkslicing, dual connectivity, interworking between NR and E-UTRA, routingof user plane data towards User Plane Function (UPF), routing of controlplane information towards Access and Mobility Management Function (AMF)and the like. As described herein, the gNBs may communicate with oneanother over an Xn interface.

The CN 106 may include at least one AMF, at least one UPF, at least oneSession Management Function (SMF), and possibly a Data Network (DN).While each of the foregoing elements are may be part of the CN 106, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF may be connected to one or more of the gNBs in the RAN 104 viaan N2 interface and may serve as a control node. For example, the AMFmay be responsible for authenticating users of the WTRUs 102 a, 102 b,102 c, support for network slicing (e.g., handling of different PDUsessions with different requirements), selecting a particular SMF,management of the registration area, termination of NAS signaling,mobility management, and the like. Network slicing may be used by theAMF in order to customize CN support for WTRUs 102 a, 102 b, 102 c basedon the types of services being utilized. For example, different networkslices may be established for different use cases such as servicesrelying on ultra-reliable low latency (URLLC) access, services relyingon enhanced massive mobile broadband (eMBB) access, services for machinetype communication (MTC) access, and/or the like. The AMF may provide acontrol plane function for switching between the RAN 104 and other RANsthat employ other radio technologies, such as LTE, LTE-A, LTE-A Pro,and/or non-3GPP access technologies such as WiFi.

The SMF may be connected to an AMF in the CN via an N11 interface. TheSMF may also be connected to a UPF in the CN 106 via an N4 interface.The SMF may select and control the UPF and configure the routing oftraffic through the UPF. The SMF may perform other functions, such asmanaging and allocating UE IP address, managing PDU sessions,controlling policy enforcement and QoS, providing downlink datanotifications, and the like. A PDU session type may be IP-based, non-IPbased, Ethernet-based, and the like.

The UPF may be connected to one or more of the gNBs in the RAN 104 viaan N3 interface, which may provide the WTRUs 102 a, 102 b, 102 c withaccess to packet-switched networks, such as the Internet 110, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andIP-enabled devices. The UPF may perform other functions, such as routingand forwarding packets, enforcing user plane policies, supportingmulti-homed PDU sessions, handling user plane QoS, buffering downlinkpackets, providing mobility anchoring, and the like.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 106 and the PSTN 108. In addition, the CN mayprovide the WTRUs 102 a, 102 b, 102 c with access to the other networks112, which may include other wired and/or wireless networks that areowned and/or operated by other service providers. In one embodiment, theWTRUs 102 a, 102 b, 102 c may be connected to a local Data Network (DN)through the UPF via the N3 interface to the UPF and an N6 interfacebetween the UPF and the DN.

As described herein and in view of FIGS. 1A-1C, and the correspondingdescription of FIGS. 1A-1C, one or more, or all, of the functionsdescribed herein with regard to one or more of: WTRU 102 a-d, BaseStation 114 a-b, eNode-B 140 a-c, MME 142, SGW 144, PGW 146, the gNB(s),the AMF(s), the UPF(s), the SMF(s), the DN(s), and/or any otherdevice(s) described herein, may be performed by one or more emulationdevices. The emulation devices may be one or more devices configured toemulate one or more, or all, of the functions described herein. Forexample, the emulation devices may be used to test other devices and/orto simulate network and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

FIG. 2 provides an example of an LTE uplink frame format for onesubframe. LTE Uplink uses a SC-FDMA scheme based DFT-s-OFDM modulation.Similar to the downlink (DL) in LTE, each subframe or transmission timeinterval (TTI) for the UL is partitioned into 14 symbols (includingcyclic prefix (CP)) and the whole system bandwidth is shared byscheduled users for UL transmissions. The frequency domain resources(RBs) at the edges of the system bandwidth are used for transmitting acontrol channel (PUCCH) and its reference channel, PUCCH RS. The rest ofthe bandwidth is used for transmitting the data channel (PUSCH) orreference channel (PUSCH RS). For example, in FIG. 2, the 4^(th) and11^(th) symbols are dedicated to the PUSCH RS, which may be used forchannel estimation at a receiver, while the remaining symbols are usedfor the PUSCH.

FIG. 3 shows an example structure for performing DFT-S-OFDM whereinmultiple DFT-spread blocks are equipped in the waveform structure. Inconventional CP DFT-S-OFDM (sometimes referred to SC-FDMA with multipleaccessing), the data symbols are first spread with a DFT block, and thenmapped to the input of an IDFT block. The CP is prepended to thebeginning of the symbol in order to avoid inter-symbol interference(ISI) and allow one-tap frequency domain equalization (FDE) at thereceiver.

The DFT-S-OFDM is an example of a precoded OFDM scheme, where theprecoding with DFT aims to reduce the PAPR. t DFT-S-OFDM is also anexample of a scheme which upsamples the data symbols by a factor equalto the ratio of the IDFT and DFT block sizes, and applies a circularpulse shaping with a Dirichlet sinc function before the CP extension. Abenefit of DFT-S-OFDM is that it exhibits lower PAPR than the plainCP-OFDM symbols.

In FIG. 3 DFT blocks 305 are used to spread incoming data d. Generally,it is desirable to have on DFT block per user in order minimize orreduce PARP. The spread data is then mapped to subcarriers and sent tothe IDFT block at 310. Next a cyclic prefix (CP) is added to the outputof the IDFT block 310, at 315.

After a set of resources (e.g. resource blocks) is allocated to a WTRU,the WTRU may choose, or be signaled, to use some resources elementswithin the allocated set of resources for sending reference signals in asubframe. For example, each user may use a few subcarriers within anOFDM/DFT-S-OFDM symbol for RSs and the rest of the subcarriers may beused to transmit DFT spread data symbols. The number of resourceelements and times may be specific to each user so that different usersmay use different numbers of resource elements at different times totransmit their RSs.

In the embodiment shown in FIG. 4, two users are allocated for uplinktransmission, and each user is granted a portion of the systembandwidth. The reference signals (shaded elements) are used in differentpatterns on different symbols between these two users. The channelcondition from the first user (user 1) to the eNB may be well enough sothat a few reference symbols are needed to achieve reliable channelestimation. While for user 2, the channel may vary fast or be noisy sothat more reference symbols are desired to achieve more reliable channelestimation. To achieve dynamic allocation of the reference signal forDFT-s-OFDM, a special DFT-S-OFDM symbol may be used.

FIG. 5 shows an example transmitter 510 and receiver 560 structures thatare capable of transmitting and receiving the proposed specialDFT-S-OFDM symbol. The transmitter 510 (for example, a UE) may have KDFT blocks, each with size M₁ 518. KM₂ reference symbols (or pilots)need to be transmitted in the frequency domain, i.e., at the input ofIDFT operation 520. To achieve this, the M₂ input of DFT block 523 maybe set to zeroes to enable interference cancellation and the M₁ input518 may be a modulated data symbol, where M₁+M₂=M. The locations of thezero symbols and the data symbols may be randomized and maybe differentthan those shown in this figure. The location of the zero samples may bechosen such that the receiver observes at least M₃+1 samples. At theoutput of each DFT block, every other M₃ samples may be discarded andreplaced by the reference symbols 530, where M₃=M₁/M₂. This may be doneby puncturing the interleaved outputs. For example, one or more outputsof the DFT block 523 may be punctured and each punctured output may bereplaced with an RS symbol. The punctured outputs may be chosen suchthat they have an interleaved pattern, (e.g. every n^(th) output isselected (n=M3)).

After replacing those samples with RS symbols, the new vector is fed tothe input of IDFT block 520. For example, when M=8 and M₂=2 referencesymbols {r₁,r₂} are needed for 8 subcarriers. Then, the input of the DFTblock may be {d₁, d₂, . . . , d₆, 0,0} (in this case M₁=6). When {x₁,x₂, . . . , x₈} is the output of DFT, after discarding every otherM₃=8/2=4 DFT outputs and replacing them by {r₁,r₂}, one gets{r₁,x₂,x₃,x₄,r₂,x₆,x₇,x₈}, which will be fed to IDFT block to generatetime domain signals. Note that the reference symbols may also beinserted with an offset, e.g., {x₁,r₁,x₃,x₄,x₅,r₂,x₇,x₈} when S=1.Finally, a CP 535 is appended to the output of the IDFT block 520.

At the receiver side 560, up to the IDFT operations 564, the signalprocessing is similar to the receiver for DFT-S-OFDM signals. Thesubcarriers that carry the reference signals at the output of DFT blocksmay be used for channel estimation. In addition, if the subcarriers thatare discarded at the transmitter side are not replaced by referencesignals (i.e., replaced by zeros), the corresponding subcarriers at thereceiver DFT output 570 may be used for noise or interference powerestimation.

Since some of the DFT block outputs are replaced by the reference symbolor pilots at the transmitter side, the output of the IDFT at thereceiver side is interfered with due to “nulling” operation 575.However, the interference may be recovered from the M₂ outputs 577 ofthe IDFT blocks and may be used to remove the interference at the otheroutput of the IDFT blocks. This process may be done in the “IC” blocks580. As an example, the structure of the IC block 580 is given in FIG. 6for a zero offset (i.e., S=0). The IC block 580 may also be improvedwith an iterative receiver architecture.

In another exemplary embodiment, the reference symbols r_(ij) shown inFIG. 5 may also be replaced by data symbols if some of the data symbolsneed to be transmitted in frequency domain. Therefore, the systemarchitecture shown in FIG. 5 allows transmitting DFT-S-OFDM and OFDMsignals simultaneously.

In another embodiment, consider a single-user scenario consisting of atransmitter and a receiver communicating over a wireless channel. Datasymbols to be transmitted within one DFT-s-OFDM symbol may be theelements of vector d∈

^(N) ^(d) ^(×1), where N_(d) is the number of data symbols. In basicDFT-s-OFDM, first, data symbols are mapped to the input of a DFT matrixdenoted by D∈

^(M×M) via a mapping matrix M_(t) ∈

^(M×M), where M is the DFT size and M=N_(d) as a special case. Theoutput of the DFT is then mapped to a set of subcarriers in thefrequency domain via another mapping matrix M_(f)∈

^(N×M). Without loss of generality, the mapping matrix M_(f) can beconstructed such that it allocates M localized or interleavedsubcarriers to achieve low PAPR. Finally, the output of the matrix M_(f)is converted to time domain via F^(H) as:

x=F ^(H) M _(f) DM _(t) d,  Equation (1)

where F^(H)∈

^(N×N) is the inverse DFT (IDFT) matrix and N is the number ofsubcarriers.

Let the channel impulse response (CIR) between the transmitter and thereceiver be a vector h=[h₀ h₁ . . .

], where

+1 is the number of taps. Assuming that the size of the cyclic prefix islarger than

, the received signal vector y can be expressed as:

y=Hx+n,  Equation (2)

where H∈

^(N×N) is the circular convolution matrix that models the interactionbetween the transmitted signal x and the channel h, and n∈

^(N×N)˜

(O_(N×1), σ²I_(N)) is the additive white Gaussian noise (AWGN) withvariance σ².

At the receiver, the operations applied at the transmitter are reversedby considering the impact of the multipath channel. The receiveroperation can be expressed as:

{tilde over (d)}=M _(t) ^(H) D ^(H) QMP _(f) ^(H) Fy,  Equation (3)

here {tilde over (d)}∈

^(N) ^(d) ^(×1) is the estimated data symbol vector and Q∈

^(M×M) is the equalizer, which removes the impact of the multipathchannel. The equalizer Q is a diagonal matrix and may be derived byusing the minimum mean square error (MMSE) criterion.

As can be seen in Equation (1), data symbols are spread across frequencyby the matrix D in DFT-s-OFDM. Therefore, legacy DFT-s-OFDM does notleave any room for frequency domain RSs in M-dimensional subspacespanned by M columns of F^(H). To allow the receiver to estimate thechannel, the RSs may be transmitted with another DFT-s-OFDM symbol byusing a fixed sequence (e.g., Zadoff-Chu sequences, as in LTE). However,adopting two separate DFT-s-OFDM symbols reduces the data ratesubstantially as the number of estimated coefficients needed toextrapolate channel frequency response may be significantly less than M.

In order to insert RSs at some frequency tones, one may follow differentstrategies including the following. One option is to puncture theinformation in the frequency domain by relying on the redundancyintroduced by channel coding. However, it may not yield recoverableDFT-s-OFDM signals at the receiver as the number of unknowns, i.e.,N_(d)(=M), is greater than the number of observations, i.e., M−N_(p),within one symbol after the puncturing, i.e., N_(d)=M>M−N_(p), whereN_(p)>0 is the number of punctured samples in frequency.

In another option, the number of data symbols may be reduced as N_(d)<Mand the size of D may be changed from M to N_(d) to accommodate thereference symbols within M-dimensional subspace. However, referencesymbols are generally not needed for all of the symbols in a frame orsubframe. Thus, this option causes both transmitter and receiver to needto employ a DFT block with variable sizes, likely not suitable withradix-2 FFT implementation.

In the third option, the number of data symbols N_(d)≤M is reduced whilekeeping the size of DFT as M so that the number of unknowns is less thanor equal to the number of observations after the puncturing, i.e.,N_(d)≤M−N_(p). This option does not increase the transmitter complexity.However, the puncturing implicitly causes interference to the datasymbols and it is not straightforward to recover the data symbols with alow-complexity receiver. In the following description, this challenge isovercome and it is shown that the data symbols can be recovered with alow-complexity receiver by employing the certain puncturing pattern andinserting zeros to certain locations before a DFT-spreading block at thetransmitter.

FIG. 7 shows an example of a transmitter 710 and receiver 760 forgeneralized DFT-S-OFDM with frequency domain reference symbols isdescribed. In this scheme, N_(z)=M−N_(d)≥N_(p) null symbols areintroduced 715 before DFT spreading 720 so that the number ofobservations is greater than or equal to the number of unknowns afterpuncturing N_(p) samples in frequency. The puncturing operation 730 maybe expressed with the matrix P∈

^((M-N) ^(p) ^()×M) considering that P punctures one symbol every otherN_(I) symbols at the output of the DFT 720 with an offset. Due to itsperiodic structure, the matrix P can be expressed as:

$\begin{matrix}{{P = {I_{N_{p}} \otimes \begin{bmatrix}I_{S} & \; & O_{{S \times N_{i}} - S} \\\; & O_{N_{i} \times 1} & \; \\O_{N_{i} - {S \times S}} & \; & I_{N_{i} - S}\end{bmatrix}}},} & {{Equation}\mspace{14mu} (4)}\end{matrix}$

where

$N_{p} = \frac{M}{N_{i} + 1}$

and N_(i)+1 is integer multiple of M. Without loss of generality, thepunctured vector is mapped to another vector in M-dimensional space byinserting N_(p) zeros via a nulling matrix N∈

^(M×M-N) ^(p) to accommodate frequency domain reference symbols denotedby c_(l) where l=1, 2, . . . , N_(p) (940). The reference symbols can bedistributed uniformly in frequency by the IDFT block (950) to improvechannel estimation performance at the receiver 950). In this case, onemay choose the matrix N as:

N=I _(N) _(p) ⊗[I _(N) _(i) O _(N) _(i) _(×1)]^(T).  Equation (5)

The overall transmit operation can finally be expressed as:

$\begin{matrix}{x = {\alpha \; F^{H}M_{f}{{{NPDM}_{t}\begin{bmatrix}d \\0_{N_{z} \times 1}\end{bmatrix}}.}}} & {{Equation}\mspace{14mu} (6)}\end{matrix}$

where

$\alpha = \sqrt{\frac{N_{d}}{N_{d} - N_{p}}}$

is scalar which scales the energy of x to be N_(d) after the puncturing.A CP may be affixed prior to transmission of the symbols (755).

As discussed above, the puncturing operation distorts the output ofDFT-spreading implicitly and causes significant interference on datasymbols. The interference on the data and null symbols can be expressedas:

r=D ^(H) P ^(H) PDd _(e) −d _(e),  Equation (7)

where d_(e) ∈

^(M×1) is the mapped data symbols and can be obtained as d_(e)=M_(t)[d^(H) O_(N) _(z) _(×1) ^(H)]^(H) and r∈

^(M×1) is the interference vector. The interference vector is notarbitrary as every other N_(I) output of the DFT-spread block is nulled.By using the lemma given below, one can obtain the structure of theinterference vector r.

Lemma 1 given below has two important results. First, by using Lemma 1,one can deduce that the kth element of the vector r is

$r_{k} = {p_{k}e^{2\pi \; k\; \frac{S}{M}}}$

and p_(k)=p_(k+N) _(p) . Secondly, it shows that the degrees of freedomof the interference vector r is N_(p) as p_(k)=p_(k+N) _(p) . Hence, onecan regenerate the vector r by observing only N_(p) elements of r thatcorrespond to the samples within one period of p_(k) and inferring therest of the vector r by using the relation of p_(k)=p_(k+N) _(p) . Inother words, M_(t) should be chosen such that the location of the nullsymbols captures the samples at least for one period of p_(k). Hence,Lemma 1 enlightens where to insert null symbols to allow the receiver torecover the data symbol without any distortion. For example, let M=8,S=0, and N_(p)=2, and assume that one chooses the input of the DFT blockto be (d₁, d₂, d₆, 0, 0) (i.e., N_(z)=2, M_(t)=I₈). Let (x₁, x₂, . . . ,x₈) be the output of DFT. After discarding every N_(I)=4 DFT outputs andreplacing them by (c₁,c₂), one gets {c₁,x₂,x₃,x₄,c₂,x₆,x₇,x₈}, whichwill be fed to IDFT block 750 to generate a time domain signal. At thereceiver side, there are only 6 samples related to data symbols at theoutput of IDFT block. By neglecting the impact of noise for the sake ofclarity and by using Lemma 1, one can show that the IDFT of theequalized vector d_(e) is (d₁+p₁, d₂+p₂, d₃+p₁, . . . , d₅+p₁, d₆+p₂,p₁, p₂) where the last two samples reveal the interference vector r asp_(k)=p_(k+2). On the other hand, the selection of the data vector as(0, d₁, 0, d₂, . . . d₆) does not allow the receiver to regenerate r asfirst and third samples carry the same interference sample after thepuncturing.

At the receiver side 760, up to the frequency domain de-mappingoperation, i.e., M_(f) ^(H), 763 the signal processing is the same forboth the legacy DFT-s-OFDM and the proposed scheme described herein. Asopposed to the legacy DFT-s-OFDM, the subcarriers that carry thereference signals at the output of DFT can be used for channelestimation (CHEST) 765 with the proposed scheme. By using the estimatedchannel, the data bearing subcarriers are first equalized 770 via Q∈

^(M-N) ^(p) ^(×M-N) ^(p) and the symbols at the output of equalizer arethen mapped to the input of IDFT via P^(H) 775. The output of IDFT D^(H)780 can be expressed as:

$\begin{matrix}{{{\overset{\sim}{d}}_{e} = {\frac{1}{\alpha}D^{H}P^{H}{QN}^{H}M_{f}^{H}{Fy}}},} & {{Equation}\mspace{14mu} (8)}\end{matrix}$

where {tilde over (d)}_(e) ∈

^(M×1) is the received vector which includes the impacts of noise,equalization, and puncturing. Considering the structure of theinterference due to the puncturing, a simple way to recover the datasymbols is:

{tilde over (d)}=M _(t.d) ^(H) {tilde over (d)} _(e) −RM _(t.r) ^(H){tilde over (d)} _(e)  Equation (9)

where M_(t.d)∈

^(M×N) ^(d) and M_(t.r)∈

^(M×N) ^(z) are the submatrices of M_(t) as M_(t)=[M_(t.d) M_(t,r)], andR∈

^(N) ^(d) ^(×N) ^(z) is the reconstruction matrix that calculates thedistortion due to the puncturing based on the relation of

$r_{k} = {p_{k}e^{2\pi \; k\; \frac{S}{M}}}$

and p_(k)=p_(k+N) _(p) dictated by Lemma 1. As a special case, when S=0and M_(t)=I_(M), R becomes a repetition matrix given by

R=1_(N) _(I) _(×1) ⊗I _(N) _(z) ,  Equation (10)

which simplifies the receiver structure substantially. For example, ifd_(e) is (d₁+p₁, d₂+p₂, d₃+p₁, . . . , d₅+p₁,d₆+p₂,p₁,p₂), R replicatesthe last two samples by N_(I)=3 times and one can recover the datasymbols by subtracting the replicated vector from the rest of thesamples of {tilde over (d)}_(e) as expressed in Equation (9).

Although the method discussed in above enables a low-complexityreceiver, it enhances the noise by 3 dB as two noisy observations areadded by Equation (9). One effective way of mitigating the noiseenhancement is to use an iterative receiver which aims to remove thenoise on the second part of Equation (9), i.e., distortion due to thepuncturing. To this end, for the ith iteration, the data symbols areestimated by:

{tilde over (d)} ^((i)) =M _(t.d) ^(H) {tilde over (d)} _(e) −RM _(t.r)^(H) {tilde over (d)} _(e) ^((i-1)),   Equation (11)

where {tilde over (d)}_(e) ⁽⁰⁾={tilde over (d)}_(e). The estimated datasymbols {tilde over (d)}^((i)) are then mapped to closest symbol in theconstellation by a non-linear function ƒ (⋅), i.e., demodulation, and{tilde over (d)}_(e) ^((i+1)) is prepared for the next iteration as:

$\begin{matrix}{{\overset{\sim}{d}}_{e}^{({i + 1})} = {D^{H}P^{H}{{{PDM}_{t}\begin{bmatrix}{f\left( {\overset{\sim}{d}}^{(i)} \right)} \\0_{N_{I} \times 1}\end{bmatrix}}.}}} & {{Equation}\mspace{14mu} (12)}\end{matrix}$

Since {tilde over (d)}_(e) ^((i+1)) is generated after the decision ismade by ƒ ({tilde over (d)}^((i))), it removes the noise from the secondpart of Equation (11) effectively and leads to a better estimate of{tilde over (d)} for the (i+1)th iteration.

It is important to emphasize that the proposed schemes described hereinintroduce some conditions on the puncturing pattern, the number ofreference signals N_(p), the number of null symbols N_(z), and thepattern of the null symbols. First, the receiver structures discussedabove exploit the fact that every N_(i) other output of the DFT with anoffset S are punctured. Second, N_(z)≥N_(p) must hold and the pattern ofN_(z) null symbols at input of DFT-spread block should capture at leastone period of distortion due to the puncturing to yield a recoverable aDFT-s-OFDM symbol. One simple way of doing is to consider N_(z) adjacentnull symbols.

There is also room to increase the performance of the receiver. Forexample, one simple way of improve the receiver performance is toincrease the number of null symbols more than the number of puncturedsymbols, i.e., N_(z)>N_(p). In this case, the receiver can combine thesamples to calculate a more reliable interference vector at the expenseof less spectral efficiency. The receiver structures described above mayalso be improved by including the channel coding decoder along withdemodulation on the feedback branch.

Without loss of generality, the schemes described herein can be expendedto multiple DFT blocks. In addition, if the subcarriers that arediscarded at the transmitter side are not replaced by RSs (i.e.,replaced by zeros), the corresponding subcarriers at the receiver DFToutput can also be used for noise or interference power estimation.

As mentioned above, lemma 1 will now be described. Lemma 1 (PeriodicInterference): Let (X_(n)) be a sequence of size M∈

for n=0, 1, . . . , M−1 and let (Y_(n)) be another sequence obtained byzeroing every other N_(i), N_(i)∈

elements of (X_(n)) with an offset of S, S≤N_(i), S∈

₀. Then, it is possible to decompose the IDFT of Y_(n) as:

y _(k) =x _(k) +r _(k), for n=0, . . . ,M−1,  Equation (13)

where (y_(k)) is the IDFT of (Y_(n)), (x_(k)) is the IDFT of (X_(n)),and (r_(k)) is a sequence of size M given by

${r_{k} = {p_{k}e^{2\pi \; k\; \frac{S}{M}}}},$

for k=0, . . . , M−1 where (p_(k)) is period sequence with the period of

$\frac{M}{N_{i} + 1}.$

The elements of the sequence (Y_(n)) can be expressed by using anauxiliary sequence (R_(n)) as:

$\begin{matrix}{{Y_{n} = {X_{n} + R_{n}}},{{where}\text{:}}} & {{Equation}\mspace{14mu} (14)} \\{R_{n}\overset{\Delta}{=}\left\{ {\begin{matrix}{- X_{n}} & {\frac{n - S}{N_{i} + 1} \in {\mathbb{Z}}} \\0 & {otherwise}\end{matrix}.} \right.} & {{Equation}\mspace{14mu} (15)}\end{matrix}$

Since IDFT operation is linear, the IDFT of (Y_(n)) can be expressed as(y_(k))=(x_(k))+(r_(k)), where (r_(k)) is the IDFT of (R_(n)). Theelements of (r_(k)) can be calculated as:

$\begin{matrix}\begin{matrix}{r_{k} = {\sum\limits_{n = 0}^{M - 1}{R_{n}e^{2\pi \; k\; \frac{n}{M}}}}} \\{\overset{(a)}{=}{\sum\limits_{m = 0}^{\frac{M}{N_{i} + 1} - 1}{{- X_{{{({N_{i} + 1})}m} + S}}e^{2\pi \; k\frac{{{({N_{i} + 1})}m} + S}{M}}}}} \\{\overset{\overset{(b)}{}}{=}{\underset{\underset{p_{k}\;}{}}{s_{{mod}{(\frac{M}{N_{i} + 1})}}}e^{2\pi \; k\; \frac{S}{M}}}}\end{matrix} & {{Equation}\mspace{14mu} (16)}\end{matrix}$

where (s_(m)) is the IDFT of (−X_((N) _(I) _(+1)m+S)) for

${m = 0},\ldots \mspace{14mu},{\frac{M}{N_{i} + 1} - 1.}$

In Equation 16, (a) is true because r_(n) is zero when

$\frac{n - S}{N_{i} + 1}$

is not an integer and (b) is true due to the periodicity of theexponential function

$e^{{- 2}\pi \; k\; \frac{{({N_{i} + 1})}m}{M}},$

which results in

$p_{k} = {p_{k + \frac{M}{N_{i} + 1}}.}$

In certain scenarios, when a single carrier waveform such as DFT-s-OFDMis used, all of the subcarriers within the allocated bandwidth may beused to transmit reference signal (pilot) symbols. In such atransmission mode, it may be possible to dynamically change the numberof the waveform symbols (for example DFT-s-OFDM symbols) that carryreference signals. As an example, in LTE uplink data transmission, onesubframe consists of 14 DFT-s-OFDM symbols and two of these symbols areused to transmit pilots. If a WTRU needs better channel estimation, forexample, due to mobility, it may be possible to increase the number ofsymbols for RS transmission from two to three or more.

Changing the number of pilot symbols would change the amount ofresources allocated for data transmission. As a result, the transportblock size and/or coding rate may need to be modified. In one solution,the number and location of pilot symbols may be configured by a centralcontroller such as the eNB, and/or signaled dynamically in the controlchannel for each transmission. For each of the possible number of pilotsymbols, corresponding values for the transport block size may bedefined.

FIG. 8 shows an example subframe in which, some of the symbolstransmitted within a specific time interval are generated by usingdifferent waveform numerology than the remaining symbols. In FIG. 8, thetime interval used for the first PUSCH symbol 810 is used to transmittwo DFT-s-OFDM symbols, where each DFT-s-OFDM symbol has half the symbolduration of the remaining symbols. One of the two new DFT-s-OFDM symbolsis used for reference signal transmission while the other symbol is usedfor data transmission.

When the waveform is not a single carrier waveform, for example, when itis OFDM, it may be possible to dynamically or semi-statically configurecertain subcarriers of certain OFDM symbols as data or pilotsubcarriers. The subcarriers that were used for data transmission may beconfigured to carry reference symbols, or subcarriers that were used forpilot transmission may be configured to carry data. It may be possibleto transmit a number of OFDM symbols within a specific time intervalwhere some of the OFDM symbols may be generated by using differentwaveforms and numerologies than the remaining OFDM symbols.

In FIG. 9, an example is provided where some of the subcarriers in thelast OFDM symbol of the subframe are configured to transmit referencesymbols, in addition to the subcarriers that were originally configuredto transmit reference symbols. In addition, the first two OFDM symbolshave half the duration of the remaining OFDM symbols and somesubcarriers of the first OFDM symbol are also configured for referencesymbol transmission. It should be noted that due to the differentwaveform numerologies, the first two OFDM symbols may have largersubcarrier spacing than the remaining OFDM symbols. Also, although acyclic prefix (CP) is not shown in the figure, a CP may precede eachOFDM symbol. These techniques may apply to other multicarrier waveformssuch as Windowed-OFDM, Filtered OFDM, Filterbank Multicarrier, and thelike.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1. A method for transmitting a Discrete FourierTransform-Spread-Orthogonal Frequency Division Multiple Access(DFT-S-OFDM) signal, the method comprising: setting at least one inputof a DFT to zero; performing DFT-spreading including the at least oneinput set to zero; puncturing an at least one output of theDFT-spreading; replacing the punctured outputs of the DFT spreading withadditional frequency domain symbols; and transmitting a DFT-S-OFDMsignal including the additional frequency domain symbols to a receiver.2. The method of claim 1, wherein the additional frequency domain symbolis a reference symbol (RS).
 3. The method of claim 1, wherein a numberof additional frequency domain symbols inserted is based on a channelcondition associated with the receiver.
 4. The method of claim 3,wherein on a condition that the channel condition is relatively poor,the number of additional frequency domain symbols inserted is increased.5. The method of claim 1, wherein the punctured output of the DFTspreading is interleaved.
 6. A wireless communication device configuredto transmit a discrete Fourier transform (DFT) spread signal(DFT-S-OFDM) signal, the device comprising: A processor configured to:set at least one input of a DFT to zero; perform DFT-spreading includingthe at least one input set to zero; puncture an at least one output ofthe DFT-spreading; replace the punctured outputs of the DFT spreadingwith additional frequency domain symbols; and a transmitter configuredto transmit a DFT-S-OFDM signal including the additional frequencydomain symbols to a receiver.
 7. The device of claim 6, wherein theadditional frequency domain symbol is a reference symbol (RS).
 8. Thedevice of claim 6, wherein a number of additional frequency domainsymbols inserted is based on a channel condition associated with thereceiver.
 9. The device of claim 8, wherein on a condition that thechannel condition is relatively poor, the number of additional frequencydomain symbols inserted is increased.
 10. The device of claim 1, whereinthe punctured output of the DFT spreading is interleaved. 11.-15.(canceled)